From a Tanner’s Son, to a Famous Scientist

Louis Pasteur believed he could do anything as long as he put his mind and heart into it. His inquisitiveness helped him overcome his apprehensions. Pasteur’s desire to help others and excel in the field of science paved the way for changing the course of medicinal history.

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Doctor Louis Pasteur seated surround by children and nurses, along with Doctor Leonid Ivanovich Voinov who is standing behind
Louis Pasteur and russian doctor Leonid Ivanovich Voinov, with russian children cured of rabies, 1886

Last Updated on 17 April 2021

Louis Pasteur (1822 – 1895) – Microbiologist, Chemist

Born to a relatively low-income family on December 27, 1822, Louis Pasteur was an ordinary kid. Like all kids, he wanted to play with his friends in their tannery, or a nearby river, or draw sketches of his family and playmates.

When Pasteur was a teenager, no one thought of him as an academic talent. Though he was hardworking, Pasteur was not the most excellent student.

Pasteur knew he could do better, and before reaching his twentieth birthday, he decided not only to be diligent but also to shift his focus to making a difference. He strove to get admission into École Normale Supérieur, which was a distinguished school in France. Here he excelled in science, notably in chemistry and physics. He graduated and started teaching.

While teaching chemistry at the University of Lille, Pasteur became curious as to how microbes reproduce. Scientists knew that there were microbes but did not know where they came from or how they began to exist.

Pasteur believed that these organisms had to come from another body before they could thrive. He needed something to work with, and when a nearby distillery came to him for assistance regarding the spoilage of their beet juice, he jumped at the opportunity.

The beet juice usually became adulterated during the fermentation process, and Pasteur began his tests. Looking under a microscope, he found out that certain round particles help in the successful fermentation of the juice, and the tube-like organisms were the cause of the spoilage. These harmful microorganisms can be killed off by heating the liquids at the right temperature, and immediately Pasteur advised the manufacturers to do so.

Portrait of Louis Pasteur in his laboratory using a microscope.
“Let me tell you the secret that has led me to my goal. My strength lies solely in my tenacity.”

A tragic family incident motivated Pasteur to do further studies on microbes. When one of his daughters died due to typhoid fever, Pasteur and his wife were overcome with grief. Pasteur’s thoughts as to why the doctors were not able to save his daughter brought him back to his fermentation experiment on microbes.

He wondered whether these microorganisms which were invisible to the human eye might be the cause of diseases. He also wanted to disprove what other scientists termed as, spontaneous generation. Spontaneous generation is the theory that living things can arise out of non-living matter without any intervention. Pasteur believed that this was wrong, and that living things could arise from living things only.

Pasteur boiled sugared yeast to decontaminate it and poured it onto two flasks. After sterilizing the vials, he left one of them uncovered, and it immediately became cloudy, indicating the presence of the microbes. The other vial was sealed, and it did not show the presence of any microbes.

In this way, Pasteur was able to prove that, contradictory to the explanation of the spontaneous generation, microbes could not arise in the sealed test tube.


“Never will the doctrine of spontaneous generation recover from the mortal blow struck by this simple experiment.”

Louis Pasteur

He also conducted a couple more experiments to fully support his hypothesis, and Pasteur presented these results to the people in an open display.

These findings would greatly benefit the doctors, especially in surgeries. Pasteur proposed that sterilizing medical and surgical tools, decontaminating hospitals, and washing hands before going into operation theaters, should be practiced. These precautions are taken in hospitals today, but back in the day, it wasn’t common.

His strenuous work and research took a toll on his health, and he suffered a stroke which left him partially paralyzed. From then on, he needed constant assistance to do even the simple tasks for his research and experimentation.

He started researching whether certain bacteria can help in decreasing or completely eradicating diseases. Another opportunity came when a group of farmers came up to him, asking him to help the parasites that threaten their cattle’s lives.

Pasteur determined the toxicity of the parasite and studied how they spread to other living organisms. Along with another scientist, Pasteur performed an experiment somewhat similar to his germ theory. However, this time, he tried turning it into a beneficial bacterium that could heal or make animals immune to the disease.

He found out that when a virus comes in contact with the air for a long time, it weakens and helps the body in immunization and somehow transforms it into something that makes the bodies stronger.

This discovery got Pasteur an invitation from the President of the Society of Agriculture to do a public experiment to test what is now known as the vaccine theory. Pasteur was delighted by his chance to prove that he is correct, but somehow fellow scientists thought that it was a bit rash to jump on the opportunity.

However, Pasteur decided to push through with the experiment. A flock of sheep and herd of cows were divided into two groups; one group had been injected with a weakened parasite and the other left in their present condition. Fourteen days passed, and the whole flock and herd were inoculated with a more potent virus. After three days, the unvaccinated groups of sheep and cows were either dying or already dead as compared to those who received the weaker virus, which was still alive and healthy. The public shouted their admiration to Pasteur, who was more grateful than proud of the opportunity to be heard.

Engrossed with the feeling of having been able to reach out and help others, Pasteur decided that it was time for him to look for a solution on dogs that were infected with rabies. When he was still young, Pasteur witnessed how the townspeople rescued one of his friends from a rabid wolf attack.

Since no one was sure how to treat the wound yet, the girl was brought to the local smith, so he could thrust his hot poker in the injury to stop the bleeding. As a kid, Pasteur was utterly horrified by what he saw. Because of this memory, he swore that he would look for a treatment for rabies.

Pasteur pinpointed that, while the virus could be referred to the dog’s saliva, this specific disorder is centered in the animal’s nervous system. At 60 years old, Pasteur carried out his experiment. He wished that he could collect a sample of saliva from the jaws of a rabid dog and asked for his assistants’ help. The assistants managed to seize the mad dog with foam on its mouth and placed it on a table. Pasteur, who was already old and frail, risked getting a small sample of the deadly saliva using a glass tube.

Pasteur in his lab with his colleague who is doing the experiment
Louis Pasteur (left) watching a colleague trephining a chloroformed rabbit during his research on rabies vaccination. 1885

He began his long and tedious research, which led to frustration and anxiety. The incubation time for the test animals was longer than that of his experiment with the sheep and cows, which often lasted for months. Using a rabbit as his first test subject, he injected a weaker form of the virus on its back and let it be for a few days. Next, he extracted the liquid from the rabbit and pumped it to a dog. He followed a few more injections for the next few days and found that the dog was responding well to the treatment. He also did the same to other test animals and did the same experiment.

Eventually, Pasteur experienced a breakthrough when the result of his test animals proved to be successful. All reactions were the same, which gave Pasteur great comfort, thinking that he might at last found a vaccine for rabies.

On July 7, 1885, Pasteur’s treatment was ready to be evaluated when a rabid dog bit Joseph Meister, a boy in their town. Though he was a bit uneasy at having to put his treatment to the test using a human being, his thoughts of what-ifs turned to a sense of urgency upon seeing the similar anguished face on the boy’s face as he saw in his friend’s.

Hoping that would work, Pasteur began his series of vaccination on the child and saw that he was improving every day. After his last inoculation, the boy once again became fit and healthy.

News of his triumphant occasion had spread across and reached those who were in the highest authority. In honor of his brilliant achievements, the French government built The Pasteur Institute in Paris, dedicated to studying most of the infectious diseases and vaccines.

On his death, Pasteur was given a state funeral in appreciation for his significant contributions to humanity. His tomb is located in the crypt of The Pasteur Institute. Today, Pasteur’s findings are used in everyday life. Pasteurization is the process of boiling milk to kill its bacteria and is named after Louis Pasteur. Similarly, disinfectants like Dettol and sterilizers are also everyday items. Doctors and surgeons sterilize their equipment using steam and radiation, following Pasteur’s advice.

Without a doubt, Louis Pasteur is one of the most influential scientists in the history of medicine.

Further Reading